JP5643569B2 - Control station equipment - Google Patents

Description

  The present invention relates to a control station apparatus that efficiently notifies control information indicating an allocated band when a frequency band is allocated continuously or discretely to a mobile station in communication using a plurality of streams using a plurality of antennas. .

  The standardization of the LTE (Long Term Evolution) system, which is the wireless communication system for the 3.9th generation mobile phone, is almost finished. Recently, the LTE-A (4th generation wireless communication system, which is a further development of the LTE system). Standardization of LTE-Advanced, IMT-A, etc.) has started.

  It has already been decided that DFT-S-OFDM (also referred to as Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing, SC-FDMA) is already adopted for the uplink (communication from the terminal to the control station) of the LTE system. . On the other hand, in the LTE-A system, Clustered DFT-S-OFDM (Dynamic Spectrum Control (DSC), DFT-S-OFDM with SDC (Spectrum Division) can be expected to improve cell throughput over DFT-S-OFDM. Control))), and OFDM and NxDFT-S-OFDM technologies have been proposed.

  Clustered DFT-S-OFDM and OFDM select a frequency that provides good reception quality in a usable band, and by arranging the spectrum discretely, a frequency selective diversity effect can be obtained and cell throughput can be improved. It is a method that can. NxDFT-S-OFDM is a scheme that extends the LTE scheme to a wide band as it is, and is a transmission scheme that can simultaneously transmit a plurality of DFT-S-OFDM signals.

  Also, in LTE-A, it has been decided to adopt MIMO (Multiple Input Multiple Output) technology for performing communication using a plurality of antennas even in the uplink. A maximum of four streams of MIMO transmission is being studied, and in addition, a pre-coding technique (transmission diversity) is also applied to improve communication performance.

  By the way, the allocation of the bandwidth used in the uplink and downlink (communication from the control station to the terminal) of the LTE system is performed by the control station transmitting control information in a channel called PDCCH (Physical Downlink Control CHannel) to the terminal. Notice. Here, the PDCCH includes a field indicating information related to band allocation called a DCI (Downlink Control Information) format. In the DCI format, uplink bandwidth allocation (referred to as format 0), downlink bandwidth allocation (referred to as format 1A), and discrete bandwidth allocation. There is something to use (called format 1). In addition, a format such as MIMO multiplex transmission (format 2 or the like) in which a plurality of transmission / reception antennas are used to transmit signals spatially in parallel using the same time and the same frequency is defined as a format.

  At this time, in the LTE system, the length of bits constituting each DCI format and the control information of the arranged frequency band are arranged on the PDCCH. The method of notifying the terminal of the DCI format is to acquire the DCI format arranged in the PDCCH and perform blind decoding based on the information on the bit length of the DCI format and the predefined frequency position candidate in which the PDCCH is arranged. (BD: Blind Decoding) and cyclic redundancy check (CRC: Cyclic Redundancy Check) for error detection are performed a plurality of times to detect which format has been transmitted without separate notification from the control station to the terminal. For this reason, when the formats having different data sizes indicating the bandwidth allocation information increase, the number of times of blind decoding is increased, so that data transmission takes time, resulting in an increase in overhead. In the current LTE system, in order to suppress the number of times of blind decoding, the data length is unified by padding the difference in size for some formats of bandwidth allocation information having a difference of several bits, and the number of formats The increase is suppressed.

  The bandwidth allocation information notified by the DCI format indicates PRB (Physical Resource Block) allocation information composed of 12 subcarriers. As a method of notifying PRB allocation information from the control station to the terminal, a VRB (Virtual Resource Block) obtained by indexing PRB is used, and band allocation information is notified by the VRB index. The terminal acquires band allocation information by converting the notified VRB information into PRB allocation information. (See Non-Patent Document 1)

3GPP TS 36.212 (V8.4.0) “Evolved Universal Terrestrial Radio Access (E-UTRA) Multiplexing and channel coding”

  However, when uplink MIMO is introduced in the LTE-A system, it is necessary to define DCI for the uplink, but the nature of the uplink and the downlink (in the uplink, the average transmission power of communication signals) The DCI must be determined in consideration of the difference in the instantaneous power ratio, that is, the PAPR characteristic, CM (Cubic Metric), and out-of-band radiation need to be considered.

  The present invention has been made in view of such circumstances, and determines control information related to uplink MIMO capable of minimizing deterioration in communication performance as much as possible, and a control station apparatus using the control information, A wireless communication system, a wireless communication method, and a program for causing a computer to execute the method are provided.

  The present invention is a control station apparatus that notifies, using control information transmitted to the terminal, an RB (Resource Block) used when receiving communication from the terminal using a plurality of transmission streams, and the RB used by the terminal And control information including information on pre-coating at the same time, and information for identifying the RB designation method used by the terminal is not notified. It is characterized by being identified.

  The allocated band setting means divides the continuous band into predetermined units that can be allocated, and performs continuous allocation setting in the band unit, and the control information generating means assigns a serial number to the band unit. Control information is generated based on the band unit number at the start position and the number of consecutive band units allocated.

  The information for identifying the designation method is associated with the maximum rank of a stream that can be transmitted by the terminal.

  In addition, the method for specifying the frequency position used by the terminal includes a method for specifying the number of RBs to be used continuously with the initial position of the RB to be used, and an RBG (RB Group) to be used continuously. The method includes at least two methods out of three methods: a method of designating the first position and the last position of each group, and a method of indicating whether or not each group can be used.

  In addition, the control information generating unit may be a band when the allocated band setting unit allocates a band continuously to a plurality of discontinuous bands and when a band is discretely allocated to one continuous band. The format of the control information indicating allocation is the same.

  Furthermore, the present invention provides a control station apparatus that notifies the frequency position used when a terminal communicates with a control station using control information transmitted from the control station to the terminal, and at least information related to precoding. When the terminal is operated in a single antenna transmission mode (including a terminal having only one transmission antenna and a mode in which there are a plurality of transmission antennas but operates as a single antenna transmission mode), the precoding is performed. It is characterized by specifying one of the information about.

  Furthermore, the present invention is a control station apparatus that notifies, using control information transmitted from a control station to a terminal, an RB to be used when the terminal communicates with the control station using a plurality of transmission streams. The minimum number of RBs to be allocated to the terminal is different depending on the number of streams transmitted by, and is specified by the initial position and number of RBs using the RB allocated to the terminal, and is included in the control information for transmission.

  In addition, the control station apparatus that uses the control information transmitted from the control station to the terminal to transmit the RB to be used when the terminal communicates with the control station using a number of transmission streams, the stream transmitted by each terminal The number of RBs constituting the RBG differs depending on the number, the RB assigned to the terminal is designated by a method indicating whether or not it can be used in units of RBG, and is included in the control information and transmitted.

Furthermore, the present invention is a control station apparatus that notifies, using control information transmitted from a control station to a terminal, an RB to be used when the terminal communicates with the control station using a plurality of transmission streams. The number of RBs (bandwidth) that can be allocated to the terminal is changed according to the number of streams transmitted by the terminal, and the RB to be used by the terminal is specified by a method according to the number of RBs that can be allocated and included in the control information. And transmitting.

  By applying the present invention, uplink MIMO control information can be properly communicated, and high-efficiency MIMO communication on the uplink can be realized while suppressing a decrease in throughput due to downlink control information. It becomes possible.

It is a block diagram which shows an example of the terminal by this invention. It is a block diagram which shows an example of the control station apparatus by this invention. It is a figure which shows an example of continuous RB allocation. It is a figure which shows an example of non-contiguous RBG allocation. It is a figure which shows an example of non-contiguous RBG allocation. It is a table | surface which shows an example of the rank with respect to SNR. It is a table | surface which shows an example of the frequency designation | designated method with respect to the rank used with the control station apparatus and terminal by the 1st Embodiment of this invention. It is a block diagram which shows an example of a structure of the scheduling part of the control station apparatus by the 1st Embodiment of this invention. It is a block diagram which shows an example of a structure of the frequency arrangement | positioning detection part of the terminal by the 1st Embodiment of this invention. It is a figure which shows an example of the frequency designation | designated method with respect to the maximum rank which can be used with the control station apparatus and terminal by 1st Embodiment of this invention. It is a figure which shows a common search space and a user specific search space. It is a figure which shows an aggregation level. It is a figure showing the bandwidth of PDCCH for every aggregation level. It is a figure which shows the code book of rank 2. It is a block diagram which shows an example of a structure of the terminal by the 2nd Embodiment of this invention. It is a block diagram which shows an example of a structure of the scheduling part of the control station apparatus by the 2nd Embodiment of this invention. It is a block diagram which shows an example of a structure of the scheduling part of the control station apparatus by the 3rd Embodiment of this invention. It is a block diagram which shows an example of a structure of the frequency arrangement | positioning detection part of the terminal by the 3rd Embodiment of this invention. It is a figure which shows an example of continuous RB allocation. It is a figure which shows an example of the RBG size with respect to the rank used with the control station apparatus and terminal by the 3rd Embodiment of this invention. It is a figure which shows an example of the RBG size with respect to the rank used with the control station apparatus and terminal by the 3rd Embodiment of this invention. It is a block diagram which shows an example of a structure of the scheduling part of the control station apparatus by the 4th Embodiment of this invention. It is a figure which shows an example of the bandwidth which can be used with respect to the rank used with the control station apparatus and terminal by the 4th Embodiment of this invention. It is a figure which shows RB of a frequency domain, and is a figure which shows an example in the case of dividing | segmenting a system band into a some block. It is a block diagram which shows an example of a structure of the frequency arrangement | positioning detection part of the terminal by the 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, the number of streams or the number of layers that can be transmitted simultaneously in the MIMO communication system is referred to as a rank.

  First, the radio communication system used in the present invention will be described. The wireless communication system according to the present invention includes one or more control station apparatuses and one or more terminals, and performs wireless communication therebetween. One control station apparatus constitutes one or more cells and can accommodate one or more terminals in one cell.

  FIG. 1 shows an example of a block diagram of a transmission apparatus applied to a terminal according to the present invention. However, in order to simplify the explanation, the minimum blocks necessary for explaining the present invention are shown.

  In FIG. 1, C bit sequences are input, which means that C different physical channels are simultaneously multiplexed. After the error correction coding is performed on the input bit series in the encoding units 101-1 to C, modulation such as PSK (Phase Shift Keying) and QAM (Quadrature Amplitude Modulation) is performed in the modulation units 102-1 to C-1. Done. The generated C modulated signals are input to the layer mapping unit 103 and mapped to P layers according to the designated rank P. Outputs in each layer are respectively input to DFT sections 104-1 to P-P, and converted into frequency domain signals by DFT (Discrete Fourier Transform). The precoding unit 105 has a function of performing precoding so that a diversity effect can be obtained among T antenna streams, and is output from the DFT units 104-1 to 1 -P when the rank P is lower than the number T of transmission antennas of the terminal. Precoding is performed on the frequency domain signal. The signal output from the precoding unit 105 is arranged at a predetermined frequency by the frequency arrangement units 106-1 to 106-T prepared for each transmission antenna. Information on the frequency to be arranged is given from the frequency arrangement detecting unit 115.

  The frequency arrangement detection unit 115 has a function of detecting the frequency arrangement from the input control information. The control information is detected by the radio unit 113 after down-converting the signal from the control station received by the reception antenna 112. The signal is input to the unit 114 and detected.

  The signals corresponding to the transmission antennas output from the frequency arrangement units 106-1 to 106-T are converted into time signals by the IFFT units 107-1 to T, and multiplexed with the reference signals in the reference signal multiplexing units 108-1 to T-T. The Then, cyclic prefixes are added in CP (Cyclic Prefix) insertion sections 109-1 to 109-T, and after being up-converted to radio frequencies in radio sections 110-1 to T, they are transmitted from transmitting antennas 111-1 to T-T. . However, when the CP is inserted, the same operation is possible even if it is added before the multiplexing of the reference signal. Therefore, the CP inserting units 109-1 to 109 -T are arranged before the reference signal multiplexing units 108-1 to 108 -T. Also good.

  FIG. 2 shows an example of a block diagram of a receiving apparatus applied to the control station according to each embodiment. The signal transmitted from the terminal is received by R receiving antennas 201-1 to 201-R, then down-converted by radio units 202-1 to R, and the cyclic prefix is removed by CP removing units 203-1 to R. After that, it is input to the reference signal separators 204-1 to 204-1R. However, since the same operation is possible even after the reference signal is separated at the time of CP removal, the CP removal units 203-1 to 203-R are arranged after the reference signal separation units 204-1 to R. May be. After the reference signal separation units 204-1 to 204-1R separate the data signal and the reference signal, the data signals are output to the FFT units 205-1 to R, and the reference signals are output to the propagation path state estimation unit 212. The data signals input to the FFT units 205-1 to R are frequency-converted by FFT, and the signals are extracted from the frequencies to which desired terminals are assigned by the frequency extraction units 206-1 to R. The R frequency domain signals extracted for each reception antenna are subjected to signal restoration / combination for each layer transmitted in the MIMO separation / combination unit 207, and IDFT units 208-1 to P-P for each of the P layers. And converted into a time domain signal by IDFT. Then, after the C physical channels multiplexed in the layer demapping unit 209 are separated, demodulation is performed by the demodulation units 210-1 to 210-1C, error correction is performed by the decoding unit, and transmitted from the terminal. A bit sequence of the acquired data is acquired.

  On the other hand, the reference signals separated in the reference signal separation sections 204-1 to 204-1R are input to the propagation path state estimation section 212, and received for each RB when transmitted from each transmission antenna of the terminal to each reception antenna of the control station. Quality (channel information) is measured. The obtained propagation path information is roughly classified into two applications depending on the type of reference signal used. DMRS (DeModulation Reference Signal) is a reference signal used for demodulation processing of a received signal, and propagation path information obtained by DMRS is input to a MIMO separation unit 207, and a signal of each layer is synthesized from the received signal. Used when. On the other hand, SRS (Sounding Reference Signal) is a reference signal used to determine parameters used in uplink transmission, and propagation path information obtained by SRS is input to the scheduling section 213. Based on the input propagation path information, the scheduling unit 213 determines the rank and frequency allocation used by the terminal for transmission, parameters such as MCS (Modulation and Coding Scheme) used for modulation and coding, and the like. Is input to the control signal generator 214 as control information. The control signal generation unit 214 performs processing such as error correction coding and modulation on the input control information, generates a control signal, and inputs the control signal to the radio unit. The signal input to radio section 215 is up-converted and transmitted from transmission antenna 216 to the terminal. The frequency allocation information output from the scheduling unit 213 is stored in the buffer 217. When the terminal receives a signal transmitted using the control information, the frequency allocation information is input to the frequency allocation extraction units 216-1 to 216-1R. The frequency used by the terminal can be extracted.

[First Embodiment]
In the first embodiment, a description will be given of a mode in which the designation method of the frequency position used for transmission is changed according to the rank when the terminal performs SU-MIMO.

  When transmitting on the uplink, the control station uses a frequency with a high channel gain as much as possible, and the frequency location is set so that multiple terminals use the same frequency to avoid inter-user interference. Scheduling is performed and the determined frequency position is notified to each terminal. At this time, since the downlink is used for notification of the frequency position, it is desirable to reduce the amount of information as much as possible, and different designation methods are assumed depending on the frequency position allocation method and the like.

  For example, in the LTE uplink, since signals are arranged in a continuous band on the frequency axis, an RB (Resource Block) composed of 12 subcarriers is set as a minimum unit of allocation, and an RB index at the head of the allocated band and The frequency position can be notified by a designation method called RIV (Resource Indication Value) that designates the number of consecutive RBs (hereinafter referred to as RIV method). FIG. 3 shows an example of assignment to RB indexes # 1 to # 4. In this case, in the RIV method, information such as # 1 of the head index and 4 of the number of assigned RBs is notified to the terminal as allocation information.

  On the other hand, when a signal is arranged in a discrete band on the frequency axis, since a frequency position designation method that notifies the number of consecutive RBs as in the case of the continuous arrangement cannot be performed, a different designation method is used. For example, in the downlink of LTE in which frequency allocation by discrete arrangement is possible, a method is used in which, for each allocation unit, a signal allocation band is designated as 1 and a non-allocation band is designated as 0 (hereinafter referred to as a bitmap). Called the law). When all the usable RBs are specified by the bitmap method, the amount of information becomes enormous. Therefore, the amount of information is suppressed by using an RBG (RB Group) in which one or more RBs are grouped as an allocation unit. Is done. FIG. 4 shows a case where RBG indexes ## 1 and ## 4 are assigned when the bitmap method is used. However, here, the RBG size (number of RBs per 1 RBG) is set to 2. In this case, in the bitmap method, information “01001” is notified as allocation information.

  In addition, when performing clustering with a limited number of divisions such as two divisions or three divisions in a discrete arrangement, a method of designating the frequency positions at both ends of each cluster in RB units or RBG units is also considered (hereinafter, referred to as “frequency division”) This is called the both-end designation method). FIG. 5 shows a case where the number of divisions is set to 2 and assigned to RBG indexes ## 0 to ## 1 and ## 4. In this case, in the both-end designation method, information such as ## 0 of the first index 1, ## 1 of the last index 1, ## 4 of the first index 2, and ## 4 of the last index 2 is notified as allocation information.

  As described above, the optimum designation method for specifying the frequency position differs depending on continuous arrangement, discrete arrangement, clustering, or the like. Here, in uplink MIMO, it is conceivable that clustering such as continuous arrangement or discrete arrangement may be used depending on the distance from the base station of the terminal and the quality of the propagation path that changes depending on transmission power and the like. On the other hand, there is a rank used for MIMO communication as a parameter that varies depending on the quality of the propagation path. Therefore, in this embodiment, an example in which the designation method of the plurality of frequency positions is switched according to the rank in the uplink MIMO system is shown. The rank is determined based on the eigenvalue of the propagation path matrix, the quality of the propagation path, and the like, but this embodiment will be described on the assumption that the quality of the propagation path is determined based on SNR (Signal to Noise power Ratio).

  FIG. 6 is a table showing the rank with respect to the SNR. In FIG. 6, X1 to X3 are thresholds for determining the rank from the SNR, and satisfy the relationship of X1 <X2 <X3.

  FIG. 7 is an example of a table showing a frequency position designation method for ranks. In FIG. 7, when the rank is 1 and 2, the RIV method is selected, and when the rank is 3 and 4, the bitmap method is selected. By appropriately using such a designation method, a terminal having a low SNR and requiring a high transmission power uses the RIV method used for continuous arrangement, and a terminal having a high SNR and good transmission characteristics is expected to have a discrete arrangement. The bitmap method used in the above is used. However, although the RIV method and the bitmap method are switched according to the rank here, the both-end designation method may be used as an alternative to the bitmap method, and three or more types of frequency position designation methods are ranked. It may be switched according to.

  The configuration of the scheduling unit in the control station of this embodiment is shown in FIG. Input from the propagation path state estimation unit 212 is input to the rank information determination unit 801 and the allocation information determination unit 803 in the scheduling unit 213. The rank information determination unit 801 determines in which rank each terminal performs transmission at the next uplink transmission opportunity according to the input channel state estimation value of each terminal. However, the rank is any value from 1 to the number of transmitting antennas. The output of the rank information determination unit 801 is input to the frequency position designation method determination unit 802, the allocation information determination unit 803, and the control information generation unit 804. The frequency position designation method determination unit 802 determines the terminal frequency position specification method from the table as shown in FIG. 7 according to the input rank information, and outputs it to the allocation information determination unit 803. The allocation information determination unit 803 determines the RB or RBG used by each terminal for uplink transmission according to the input channel state estimation value, rank information, and frequency location designation method of each terminal, and generates control information as allocation information. Output to the unit 804. The control information generation unit 804 generates control information from the input rank information and allocation information, information indicating a precoding matrix (not shown), and the like, and inputs the control information to the control signal generation unit 214 and the buffer 217.

  On the other hand, FIG. 9 shows the configuration of the frequency arrangement detection unit in the terminal of this embodiment. The control information input from the control information detection unit is input to the rank number information detection unit 901 and the allocation information detection unit 902. The rank number information and the allocation information are detected and input to the frequency arrangement specifying unit 903, respectively. At this time, since the frequency location specifying method used for the allocation information given from the allocation information detecting unit 902 cannot be determined, the frequency allocation specifying unit 903 confirms the frequency location specifying method based on the input rank information. I do. At this time, a table as shown in FIG. 7 is used for confirmation, but the same frequency position designation method determining unit 802 in FIG. 8 is used as the table, so that the frequency position designation method used in the control station is used. Can be recognized correctly. The frequency arrangement is specified from the allocation information by the confirmed frequency position designation method, and is input to the frequency arrangement units 106-1 to 106-P for each antenna.

  In the above example, the mode of switching the frequency location method according to the rank actually used by the terminal is shown. However, in the system where the rank of the terminal is adaptively changed depending on the transmission environment, the frequency location method is temporally changed. If it is not desirable to change, the frequency location method may be determined based on the maximum rank that can be used by the terminal. In such a case, the determination of the frequency position specifying method is performed by associating the maximum rank with the frequency position specifying method as in the table shown in FIG. In FIG. 10, when the maximum ranks that can be used by the terminal are 1 and 2, the RIV method is used, and when the maximum rank is 4, the bitmap method is used. The maximum rank value can be determined from the information of the reference signal received by the control station, but any other information that can be used by the control station may be used.

  In this embodiment, when the allocation method such as continuous arrangement or discrete arrangement changes according to the state of the propagation path, the frequency position designation method is identified by changing the frequency position designation method according to the rank in MIMO communication. It is possible to make a determination without notifying the information for doing so.

[Second Embodiment]
In this embodiment, a method for operating a terminal in the single antenna transmission mode will be described.

  In LTE-A, it is considered to define three transmission modes in the uplink. The first is Rel-8 single antenna transmission mode for the purpose of maintaining backward compatibility with LTE, the second is Rel-10 single antenna transmission mode that can support Clustered DFT-S-OFDM, and the third is multiple This is a MIMO transmission mode in which transmission is performed using the transmission antennas. Here, Rel-8 supports the same communication method as LTE, and Rel-10 uses the same communication method as LTE and LTE-A that is newly adopted. For these transmission modes, control information for radio transmission is notified to each terminal using a downlink PDCCH.

  Next, an LTE-A control channel reception method will be described. Each terminal detects control information addressed to itself using a technique called blind decoding. The PDCCH uses a frequency region that can be detected by all terminals for the purpose of preventing communication disconnection due to transmission mode switching called a common search space (CSS) in the system bandwidth, and each transmission mode. It is arranged in a frequency region called user specific search space (USSS) in which control information addressed to the terminal is arranged.

  FIG. 11 shows the concept of the common search space and the user-specific search space. Here, a case where the system bandwidth is 20 MHz will be described as an example. In this case, the number of subcarriers is 1200, and the number of CCEs is 33. First, in the frequency domain, 4 subcarriers are defined as 1 REG (Resource Element Group), and 9 REG is defined as 1 CCE (Control Channel Element). That is, one CCE is composed of 36 subcarriers. Reference numeral 1101 in FIG. 11 denotes a frequency region indicating a common search space, which is arranged at 16 CCE from the head frequency of the system band. Reference numeral 1102 in FIG. 11 represents a user-specific search space, and any CCE can be assigned. Next, a method for arranging PDCCH in each search space will be described. In order to ensure coverage, PDCCH can set an aggregation level for changing the allocated bandwidth so that the coding rate can be changed according to the required quality. FIG. 12 shows the aggregation level. When the distance from the control station is short, the control information can be transmitted with a small amount of radio resources by using the aggregation levels 1 and 2, and when the distance from the control station is far, the aggregation levels 4 and 8 are many. By using the wireless resource, control information can be notified at a low coding rate, and coverage can be ensured.

  When placed in the common search space, aggregation level 4 or 8 is set, and when placed in the user-specific search space, an arbitrary aggregation level is selected according to the required quality, for each aggregation level, for each terminal. The value set by the hash function for each subframe is set as the start position of the PDCCH arrangement. FIG. 13 shows the concept of the arrangement of user-specific search spaces. Aggregation level 1 is 1301, aggregation level 2 is 1302, aggregation level 4 is 1303, and aggregation level 8 is 1304. At this time, a CCE where mod (i, L) = 0 at each aggregation level is set as the head. However, i is a CCE number, L is an aggregation level, and mod is a remainder operation.

  Each terminal searches for the PDCCH arranged in this way, and the terminal decodes based on the candidate number of bits of control information and all frequency candidates. When the number of bits is the same, it is identified by a flag or user ID included in the control information. This is the blind decoding described in the background art. It is considered that the number of times of this blind decoding varies depending on the transmission mode. It is considered that the Rel-8 single antenna transmission mode and the Rel-10 single antenna transmission mode are 44 times and the MIMO transmission mode is 60 times. ing.

  This is because the Rel-8 and Rel-10 single antenna transmission modes must be notified with the same number of bits of control information, and the Rel-10 single antenna transmission mode has the same amount of control information as Rel-8. There is a problem that the number of clusters that can be supported is reduced due to the restriction of information bits related to frequency arrangement. On the other hand, in the MIMO transmission mode, the number of times of blind decoding is 60, which is larger than that in the single antenna transmission mode, which means that new control information may be specified.

  In general, it is already known that Clustered DFT-S-OFDM increases as the number of clusters that can be supported increases, and the throughput decreases due to control information of the Rel-10 single antenna transmission mode. However, in the MIMO transmission mode, since the number of times of blind decoding is large, it is considered that the number of clusters that can be supported is large. Therefore, even when operating in the single antenna transmission mode, if control information used in the MIMO transmission mode can be notified, the number of terminals in the single antenna transmission mode that can support a large number of clusters increases, improving the efficiency of the entire system. can do.

  Next, in the MIMO transmission mode, a precoder is defined that controls a base station to receive a signal in the same phase when transmitting by a plurality of transmission antennas. FIG. 14 shows precoding parameters used when the number of transmission antennas is two. Number of Layers υ indicates the number of signals to be spatially multiplexed. When υ = 1, the same signal is assigned to the two transmission antennas, and the array gain (beam gain) is selected from the vectors of υ = 1. ) Is selected, and the transmission signal is multiplied and transmitted. When υ = 2, since it is a unit matrix, different signals are transmitted as they are from the respective antennas. Here, the codebook indexes 4 and 5 of the number of layers 1 mean that nothing is transmitted from one transmission antenna. This should be applied when the attenuation between transmission antennas is greatly different (AGI; Antenna Gain Imbalance), but it is substantially the same as the single antenna transmission mode, and this is notified in the single antenna transmission mode. For example, a single antenna transmission mode with a large number of clusters can be realized.

  FIG. 15 shows an example of a block diagram of a transmission device applied to the terminal according to the embodiment. Control information received by the receiving antenna 1510 is converted into a baseband signal by the radio unit 1511, and control information is obtained by the PDCCH detection unit 1512. Next, the control information detection unit 1514 detects various types of information such as MCS and frequency allocation information included in the control information. At this time, first, the code book index detection unit 1513 detects whether the terminal has the code book indexes 4 and 5. Next, when the codebook indexes 4 and 5 exist in the terminal, information on whether or not they exist is input to the control information detection unit 1514. The control information detection unit 1514 detects information related to frequency allocation based on information on whether or not the codebook indexes 4 and 5 exist, and the frequency allocation detection unit 1515 determines the frequency allocation.

  In this embodiment, the MIMO transmission mode and the single antenna transmission mode may differ in the information source encoding method of the frequency allocation information. Therefore, the codebook index is detected first, and the frequency allocation is performed from the bit string based on the information. It is configured to detect information. Based on these pieces of control information, the terminal performs error correction coding on the bit sequence by the coding unit 1501 and converts it into a modulation symbol by the modulation unit 1502. Next, it is converted into a frequency signal by the DFT unit 1503 and is arranged at the frequency based on the frequency allocation information notified by the frequency arrangement unit 1504. Thereafter, the IFFT unit 1505 converts the signal into a time signal by IFFT, and the reference signal multiplexing unit 1506 multiplexes the reference signal. Finally, a CP is inserted by the CP insertion unit 1507, up-converted to a radio signal by the radio unit 1508, and transmitted from the transmission antenna 1509.

  FIG. 16 shows an example of the configuration of the scheduling unit 213 of the control station apparatus. Scheduling section 213 selects a codebook that stops one of the antennas in codebook index determination section 1601 according to the transmission mode based on the information on the propagation path state input from propagation path state estimation section 212, and assigns it. The information determination unit 1602 determines allocation information. Next, control information generation section 1603 generates control information from the information output from codebook index determination section 1601 and allocation information determination section 1602, and inputs the control information to control signal generation section 214 and buffer 217.

  The point of this embodiment is that it is a single antenna transmission, has a means for detecting a codebook index, and is notified using the codebook indexes 4 and 5. As a result, the number of clusters that can be supported in the single antenna transmission mode is increased, so that the throughput can be increased. The present invention may have any number of transmission antennas, and selects a codebook index in which only one of all transmission antennas is transmitted, and notifies the terminal device to operate as a single antenna transmission mode. And

[Third Embodiment]
In this embodiment, a method of changing the minimum number of assigned RBs or RBGs according to the rank when the terminal performs SU-MIMO will be described.

  The configurations of the transmission device applied to the terminal according to the present embodiment and the reception device applied to the control station are the same as those in FIGS. 1 and 2. The frequency band used by the terminal for data transmission is determined by the scheduling unit 213 of the control station, and the scheduling unit 213 has the configuration shown in FIG. The scheduling unit 213 receives the channel information estimated by the channel state estimation unit 212, and the channel information is input to the rank information determination unit 801 and the allocation information determination unit 1702. As in FIG. 8 in the first embodiment, the rank information determination unit 801 determines the rank used for uplink transmission based on the propagation path information of each antenna. Here, the rank may be changed every time scheduling is performed, or may be changed at a constant cycle. The determined rank is input to the control information generation unit 803 and the allocation information determination unit 1702. The allocation information determination unit 1702 receives propagation path information and rank information, changes the minimum number of allocated RBs or RBGs according to the rank, and determines the frequency position allocated to the terminal.

  On the other hand, FIG. 18 shows the configuration of the frequency arrangement detection unit 115 in the terminal of this embodiment. The frequency arrangement detection unit 115 has the same block configuration as that of FIG. 9 in the first embodiment, but differs in that the frequency arrangement specifying unit 903 is a frequency arrangement specifying unit 1803. The frequency arrangement specifying unit 1803 determines the minimum number of assigned RBs or RBGs based on the input rank information. Here, the minimum allocation number of RBs or the number of RBGs is determined based on the same definition as the allocation information determination unit 1702 of the control station, so that the frequency allocation can be correctly specified.

Here, an example will be described in which the frequency allocation to the terminal is a continuous frequency band, and the base station notifies the terminal of the frequency position with the allocation starting RB and the number of RBs allocated in FIG. In this case, allocation start RBs can indicate all RBs, and the number of RBs to be allocated can be specified in units of 1 RB. Therefore, the minimum number of assigned RBs is 1 RB. By assigning an arbitrary frequency in such 1 RB units, it becomes possible to select and assign a frequency having a higher propagation path gain. On the other hand, since a higher rank is selected for a terminal having a high channel gain, more data can be transmitted per RB. In addition, a terminal that needs data transmission at a higher rank may transmit a lot of data. Therefore, the higher the rank, the better the propagation path and the more data transmission is required, so the minimum number of assigned RBs is determined as shown in the table shown in FIG. However, r ₁ <r ₂ <r ₃ <r ₄ is satisfied, and RB _min (1) <RB _min (2) <RB _min (3) <RB _min (4) is satisfied. As an example, if the rank r _i is 2 and the minimum number of assigned RBs RB _min (i) is 4 RBs in this case, if the allocation start RB in FIG. Means that an assignment is made. When the rank is 1, the minimum number of assigned RBs is reduced, for example, the minimum number of assigned RBs RB _min (i) is set to 2 RBs or 1 RB as in the conventional case.

In the above example, the number of allocated RBs N _alloc of rank r _i is an integer that satisfies the following expression.
However, N _{sys — rb} is the total number of RBs that can be allocated, and in FIG. 19, the total number of RBs is 20. The allocated RB number N _alloc may be limited as follows according to the rank r _i .
However, m is an integer of 1 or more.

The above is an example of determining N _alloc , and is not limited to an integer multiple of RB _min (i) in the case of rank r _i . Therefore, N _alloc may be an integer multiple of RB _granularity that satisfies the following equation.
For example, the rank r _i may be 2, the minimum number of assigned RBs RB _min (i) may be 4 RBs, and the RB _granularity may be 2 RBs.

As another method of specifying the frequency position used by the terminal, an example will be described in which one or more RBs are RBGs and the assigned frequency position is notified in RBG units. The number of RBs constituting a conventional RBG is determined by the system bandwidth, that is, the number of RBs that can be allocated. However, since a higher-rank terminal that transmits more data requires more RBs, the size of the RBG may be large. On the other hand, it is preferable that a low-rank terminal has a high frequency selectivity and a small RBG size. Therefore, the RBG size is determined according to the rank as shown in the table of FIG. _However, the _{r 1 <r 2 <r 3} <r 4, shall meet the _{RBG size1 <RBG size2 <RBG size3} <RBG size4. For example, when the rank is 2, the number of RBs constituting the RBG is 4, and when the rank is 1, the number of RBs constituting the RBG is 1.

  In this embodiment, the minimum number of assigned RBs or the size of the RBG is changed according to the rank, and a terminal having a lower rank can obtain a frequency selection diversity effect by reducing the minimum size that can be assigned. Can be improved. On the other hand, a higher-rank terminal that needs more data transmission can allocate a band with a small amount of control information, and the overhead is reduced, so that the throughput of the entire cell can be improved.

[Fourth Embodiment]
In the present embodiment, a case will be described where the upper limit value of the number of RBs that can be used differs according to the rank when the terminal performs SU-MIMO.

  The configurations of the transmission device applied to the terminal according to the present embodiment and the reception device applied to the control station are the same as those in FIGS. 1 and 2. However, the function in the frequency arrangement detection unit 115 shown in FIG. 1 and a part of the function in the scheduling unit 213 shown in FIG. 2 are different from those in the other embodiments.

  The configuration of the scheduling unit 213 in the present embodiment is shown in FIG. FIG. 22 includes the same blocks as the scheduling unit of FIG. 17 in the third embodiment, but the allocation information determination unit 1702 is the allocation information determination unit 2202 and has different functions. The input from the propagation path state estimation unit 212 is input to the rank information determination unit 801 in the scheduling unit 213. Rank information determination section 801 determines the rank at which each terminal performs transmission at the next uplink transmission opportunity using the input channel state estimation value of each transmission antenna of each terminal. . The rank is any value from 1 to the number of transmission antennas. The output of the rank information determination unit 801 is input to the allocation information determination unit 2202 and the control information generation unit 803. The allocation information determination unit 2202 also receives the reception quality for each RB at each transmission antenna from the propagation path state estimation unit 212. Allocation information determination section 2202 determines allocation using the reception quality estimation value and rank information for each RB in each transmission antenna. The allocation criteria will be described later. The output of the allocation information determination unit 2202 is input to the control information generation unit 803. The control information generation unit 803 generates control information by combining the input rank information and allocation information, PMI indicating a precoding matrix (not shown), and inputs the control information to the control signal generation unit 214 and the buffer 217.

Here, in the uplink of LTE, the maximum value of the number of RBs that can be allocated is defined as N _RB ^{max, UL} . That is, the allocation information determination unit in LTE determines allocation so as not to exceed N _RB ^{max, UL} . Therefore, in this embodiment, the maximum value of the number of RBs that can be allocated is limited by the rank or the like. For example, the rank R, when the number of used transmit antennas and N _t, defines the assigned maximum possible value of the number of RB as follows.
In this way, by limiting the maximum value of the number of RBs that can be allocated, the maximum value is lowered when the rank is low, so that the amount of allocation information can be reduced. Further, the limiting method is not limited to Equation 1 ^, and any method may be used as long as the number of RBs that can be allocated is determined from N _RB ^{max, UL} and R. Moreover, the form designated using the table predetermined by transmission / reception like FIG. 23 may be sufficient.
Note that the maximum number of RBs that can be allocated does not have to be different for each rank. For example, as shown in FIG. 23, the same maximum number of RBs that can be assigned in rank 3 and rank 4 may be used.

  The example of limiting the maximum number of allocations in the terminal has been described above, but the allocation method of the allocation information determination unit when limiting the range of frequencies that can be allocated next will be described with reference to FIG. In FIG. 24, numerical boxes represent allocation units (RB or RBG) in the system band.

  In the present embodiment, the bandwidth that can be allocated is limited by the rank input from the rank information determination unit 801 to the allocation information determination unit 2202. For example, when the rank information determining unit 801 notifies the allocation information determining unit 2202 that the rank of a certain terminal is 4, as shown in FIG. 24, the entire system band is an allocation candidate. Therefore, allocation can use all of RB0 to RB19. Note that the assignment may be discrete or continuous. Also, when the rank information determination unit 801 notifies that the rank is 3, in the example of FIG. 24, the block 0 is an allocation target. On the other hand, when it is notified from the rank information determination unit 801 that the rank is 2, the RBGs that are candidates for allocation are limited. In the example of FIG. 24, rank 2 is assigned up to block 0 (RB0 to RB9) corresponding to ½ of the system bandwidth. Also, as shown in FIG. 24, block B (RB10 to RB19) may be assigned. The control station can effectively use the system band by notifying the terminal from which range of block A or block B allocation is performed. Further, instead of performing notification, designation may be performed by a method determined in advance by transmission and reception. For example, block A is assigned when the number of assigned RBs is an odd number, and block B is assigned when the number is even, or a cyclic shift value given to each terminal (LTE specifies one of eight values). It is possible to notify the used block without wasting the notification information by dividing it into even numbers or odd numbers. When the rank is 1, allocation is performed in the range of four blocks, block 0 to block 3, in the example of FIG. As shown in FIG. 24, the size of each block may be different or the same. In FIG. 24, three allocation restriction categories of rank 1, rank 2, and ranks 3 and 4 are provided. However, there is no need to use three, and different restrictions may be applied to each of the four. Two divisions of ranks 2 to 4 may be provided to perform restriction. Further, although block A and block B do not overlap in FIG. 24, a part of the allocation range of each block may overlap.

  As described above, the control station of the present embodiment limits frequency allocation according to rank information. This information is also shared by the terminals, and the frequency arrangement detection unit 115 of FIG. 1 of the terminals first detects the rank and changes the frequency allocation information decoding method according to the rank. FIG. 25 shows the configuration of the frequency arrangement detection unit 115 in the terminal of this embodiment. The frequency arrangement detection unit 115 has the same block configuration as that in FIG. 9 in the first embodiment, but differs in that the frequency arrangement specification unit 903 is a frequency arrangement specification unit 2503. The frequency arrangement specifying unit 2503 confirms the maximum number of RBs that can be assigned based on the input rank information. At this time, the confirmation is performed based on the same definition as that of the allocation information determination unit 2202 of the control station, so that the frequency arrangement can be correctly specified.

  In this embodiment, the allocation range is limited according to the rank as described above. By performing such processing, it is possible to reduce the overhead when the control station device notifies the terminal device of the allocation information, and the system throughput can be improved.

  In each of the above embodiments, for convenience of explanation, the case where the base station apparatus and the mobile station apparatus are one-to-one has been described as an example, but there may be a plurality of base station apparatuses and mobile station apparatuses. Further, the mobile station device is not limited to a moving terminal, and may be realized by mounting the function of the mobile station device on a base station device or a fixed terminal.

[Modification]
In each of the embodiments described above, a program that operates on a terminal and a control station apparatus related to the present invention is a program that controls a CPU or the like (a computer is installed) so as to realize the functions of the above-described embodiments related to the present invention. Program to function). Information handled by these devices is temporarily stored in the RAM at the time of processing, then stored in various ROMs and HDDs, read out by the CPU, and corrected and written as necessary. As a recording medium for storing the program, a semiconductor medium (for example, ROM, nonvolatile memory card, etc.), an optical recording medium (for example, DVD, MO, MD, CD, BD, etc.), a magnetic recording medium (for example, magnetic tape, Any of a flexible disk etc. may be sufficient. In addition, by executing the loaded program, not only the functions of the above-described embodiment are realized, but also based on the instructions of the program, the processing is performed in cooperation with the operating system or other application programs. The functions of the invention may be realized.

  In the case of distribution in the market, the program can be stored and distributed in a portable recording medium, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is also included in the present invention. Moreover, you may implement | achieve part or all of the terminal in the embodiment mentioned above and the control station apparatus as LSI which is typically an integrated circuit. Each functional block of the mobile station apparatus and the base station apparatus may be individually chipped, or a part or all of them may be integrated into a chip. Further, the method of circuit integration is not limited to LSI, and may be realized by an ASIC, a chip set substrate, a dedicated circuit, or a general-purpose processor. In addition, when an integrated circuit technology that replaces LSI appears due to the advancement of semiconductor technology, an integrated circuit based on the technology can be used.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and the design and the like within the scope of the present invention are also within the scope of the claims. include.

101-1 to C: encoding unit, 102-1 to C ... modulating unit, 103 ... layer mapping unit, 104-1 to P ... DFT unit, 105 ... precoding unit, 106-1 to T ... frequency allocation unit, 107 -1 to T: IFFT unit, 108-1 to T ... reference signal multiplexing unit, 109-1 to T ... CP insertion unit, 110-1 to T ... radio unit, 111-1 to T ... transmission antenna, 112 ... reception Antenna 113 113 wireless unit 114 control information detection unit 115 frequency arrangement detection unit 201-1 to R reception antenna 202-1 to R radio unit 203-1 to R CP removal unit 204 -1 to R: reference signal separation unit, 205-1 to R ... FFT unit, 206-1 to R ... FFT unit, 207 ... MIMO separation / synthesis unit, 208-1 to P ... IDFT unit, 209 ... layer demapping Part, 210-1 to C ... demodulation part 211-1 to C: decoding unit, 212: propagation path state estimation unit, 213 ... scheduling unit, 214 ... control signal generation unit, 215 ... radio unit, 216 ... reception antenna, 217 ... buffer, 801 ... rank information determination unit, 802 ... Frequency position designation method determining unit, 803 ... Allocation information determining unit, 804 ... Control information generating unit, 901 ... Rank information detecting unit, 902 ... Allocation information detecting unit, 903 ... Frequency allocation specifying unit, 1101 ... Common search space, 1102 ... User-specific search space, 1301 ... Aggregation level 1, 1302 ... Aggregation level 2, 1303 ... Aggregation level 4, 1304 ... Aggregation level 8, 1501 ... Code part, 1502 ... Modulation part, 1503 ... DFT part, 1504 ... Frequency arrangement Part, 1505 ... IFFT part, 1506 ... see Signal multiplexing unit, 1507 ... CP insertion unit, 1508 ... radio unit, 1509 ... transmission antenna, 1510 ... reception antenna, 1511 ... radio unit, 1512 ... PDCCH detection unit, 1513 ... codebook index detection unit, 1514 ... control information detection unit , 1515 ... frequency allocation detection unit, 1601 ... codebook index determination unit, 1602 ... allocation information determination unit, 1603 ... control information generation unit, 1702 ... allocation information determination unit, 1803 ... frequency allocation specification unit, 2202 ... allocation information determination unit , 2503 ... Frequency arrangement specifying unit

Claims (6)

A terminal device comprising a plurality of transmission antennas and performing communication with a control station device,
A PDCCH detector that detects control information from a signal received from the control station device;
A codebook index detection unit for detecting a codebook index from the control information;
A frequency arrangement detection unit for detecting frequency arrangement information from the control information;
One transmission mode is set from a plurality of transmission modes including a first transmission mode corresponding to single antenna transmission and a second transmission mode corresponding to MIMO transmission, and DFT-S- is set based on the frequency arrangement information. A transmission unit that performs transmission using OFDM or Clustered-DFT-S-OFDM,
The transmitter performs single antenna transmission when the first transmission mode is set or when the second transmission mode is set and the codebook index is a predetermined value.
A terminal device characterized by that. The PDCCH detector is
The number of times of blind decoding for detecting control information is greater when the second transmission mode is set than when the first transmission mode is set.
The terminal device according to claim 1. The frequency arrangement information detected when using the second transmission mode is the number of clusters supported in the Clustered DFT-S-OFDM compared to the frequency arrangement information detected when using the first transmission mode. There are many
The terminal device according to claim 1. A control station apparatus that receives a signal from a terminal apparatus having a plurality of transmission antennas,
A codebook index determining unit that determines a codebook index used by the terminal device for transmission;
An allocation information determining unit that determines a frequency arrangement used by the terminal device for transmission;
A control information generating unit that generates control information for notifying the terminal device of the codebook index and the frequency allocation;
When the codebook index determining unit instructs the terminal apparatus to perform single antenna transmission in a transmission mode corresponding to MIMO transmission, the codebook index is stopped except for one of the plurality of transmission antennas. Decide
A control station apparatus. A wireless communication method used for a terminal device having a plurality of transmission antennas,
One transmission mode is set from a plurality of transmission modes including a first transmission mode corresponding to single antenna transmission and a second transmission mode corresponding to MIMO transmission, and DFT-S-OFDM or Clustered DFT-S. -Transmit using OFDM,
In the second transmission mode, control information including frequency allocation information and precoding index is received from the control station apparatus, and when the precoding index is a predetermined value, single antenna transmission is performed.
A wireless communication method. An integrated circuit mounted on a terminal device having a plurality of transmission antennas,
One transmission mode is set from a plurality of transmission modes including a first transmission mode corresponding to single antenna transmission and a second transmission mode corresponding to MIMO transmission, and DFT-S-OFDM or Clustered DFT-S. A function to transmit using OFDM;
A function of receiving control information including frequency allocation information and precoding index simultaneously from the control station apparatus in the second transmission mode, and performing single antenna transmission when the precoding index is a predetermined value; , Causing the terminal device to exhibit a series of functions including
An integrated circuit characterized by that.